Control valve for fluid servomotors



Oct. 17, 1950 a JOHNSON CONTROL VALVE FOR FLUID SBRVOHOTORS Original Filed March 2, 1944 Q05 $.00 QM S CLARENCE JOHNSON Gtforncg FIG.2

Patented. Oct. 17, 1950 v Clarence Johnson, South Euclid, Ohio, assignor to Bailey Meter Company, a corporation of Delaware Original application March 2, 1944, Serial No. 524,797, now Patent No. 2,475,929, dated July 5, 1949. Divided and this application May 29, 1949, Serial No. 672,992

4 Claims. (01.- 1z1-4es) This invention relates in general to fluid control valves and more especially to fluid pilot valves for use with fluid servo-motors.

An object of the invention is to provide a fluid pilot valve to direct fluid to one end or the other of the cylinder of afluid servo-motor.

A further object of the invention is to construct such a fluid pilot valve which has a minimum of friction and which has a minute continuous fluid leakage therein to, prevent a build up of pressure on one side of the piston of the fluid servo-motor relative to the other.

A still further object of the invention is to provide a fluid pilot valve which is very easily reciprocably positioned and which has no undesirable end reaction or tendency for axial displacement.

A still further object of the invention is to provide a fluid pilot valve which may be easily axially positioned by a low powered air pressure system wherein the pilot valve and associated fluid servo-motor create no self-energizing axial movement to'cause a load on the low powered air pressure system.

The fluid pilot valve of the invention may be used with any fluid servo-motor and is preferablly adapted for use with contour control systems for use with material forming machines such as may be found in my parent Patent No. 2,372,426.

In the drawing:

Fig. 1 is a front elevation, partly in section, of a pilot valve assembly of the invention;

Fig. 2 is an enlarged sectional elevation of the pilot valve of Fig. l; and

Fig. 3 is a sectional view of the stationary pilot valve sleeve of Fig. 2.

The fluid pilot valve will be described in conjunction with an assembly which includes a low pressure air system for positioning the movable portion of the pilot valve. Such a low pressure air system is often found on contour control systems of material forming machines wherein an air tracer obtains intelligence from a pattern or template and the variations of air pressure obtain in the air tracer are used to axially position a bellows with such bellows positioning the movable member of the fluid pilot valve. The fluid pilot valve may then direct fluid to one end or the other of a cylinder of a fluid servomotor which is the power means for moving a machine element of the material forming machine to cause such machine element to follow the dictates of the pattern.

In Figure l, I show an elevation, partly in section, of the complete assembly 29 to approximately one-half scale. In Fig. 2 I show to approximatel full scale a sectional elevation of the relay valve itself, and in Fig. 3 a sectional view of the pilot valve sleeve to still larger scale.

Air pressure, as determined by the tracer assembly, is available through the pipe 99 and effective upon the bellows 21 for positioning the free end 94 therefor as well as the movable containing cup- 95. Positioned by the bellows '21 is a relay valve member 99 relative to a stationary sleeve member 91. The sleeve 91 is mounted within a housing ii, and may be axially positioned therein by the threaded end caps 92 and 99. Loading the bellows, or opposing movement of the bellows and the valve member 99, is a spring 99 adjustablv supported at one end and pivotally fastened at its movable 'end, as at 99,

to one end of a yoke 99 straddling the air inlet pipe 99 and bellows containing cup-95. At its lower end the yoke 99 is fastened to the bellows containing cup 95, and is also attached to the upper ball joint 9|. The relay valve member 99 is positioned by a wire or small rod connection 92 joining the upper ball joint 9| with a lower ball joint, the latter of which is adiistably connected to the relay valve member 9 Due to the design of the valve member 99, it is positionable with substantially no friction or end thrust reaction, and thus imposes substantially no load upon the positioning rod 92. The driving construction including the ball joints 9|, 99 and rod 92 minimized the efl'ect of any slight misalignment of the parts or distorted movement of the power unit comprising the spring 99, the yoke 99, bellows 21 and the containing cup 95. The construction of the ball joint 99 is clearly shown in Fig. 2 wherein the ball retaining cap 94 may be of metal for example and may be lubricated. The ball joint 9i is of similar construction. Obviously, the compression of the cap 94 upon the ball'may be readily adjusted.

The movable valve member 96 is provided with three spaced lands 99, 99 and 91 and is positionable within the bore 99 of the stationary sleeve 91. In my preferred construction the upper and lower lands 95, 91 have a diameter allowing a total clearance of approximately .001 inch with the bore 99, while the middle land 99 may have slightly less clearance with the bore 011 under pressure is available through the pipe 34 in an annular chamber (see Fig. 3) surrounding the sleeve 01 at the location of the land 90 and communicating with the bore 00 through a plurality (in this example four) of openings I00. The width of the land 00 is preferably about .002 inch less than the diameter of the holes I00 so that when the" member 05 is in its neutral position, with the land it centered on the holes I00, there may be a very slight bleed of oil from the annular chamber 00 through the holes III to either side of the land 95 within the bore 00.

In the preferred embodiment, the sleeve 81 has two drainage openings IN and two drainage openings I02, each of roughly triangular shape. The number and shape of these openings may vary for difierent conditions. They communicate respectively with annular chambers I03, I04, which drain to the sump through pipe or pipes 31.

With the member 06 in neuiu'al position the lands 95, 91 are so spaced relative to drainage openings IOI, I02 that the tip of each such opening is uncovered by approximately .002 inch providing thereby a continuous small bleed of oil from the interior of the bore 00 between the lands 95, 95 and between the lands 95, 31.

Intermediate the lands 95, 95 in thesleeve 01 are a, plurality of openings I05 communicating with an annular chamber I00 to which is joined the pipe 36 leading to one end of the cylinder of the servo-motor. Intermediate the lands 05, 91 in the sleeve 81 are a plurality of openings I01 communicating with an annular chamber. I00, which is joined by the pipe 35 leading to the other end of the cylinder of the servo-motor.

The operation is as follows:

.1. With the valve member 05 in what I term a neutral position (for cylindrical turning) the piston of the servo-motor is locked by equal oil pressures on opposite sides thereof against movement. A minute constant flow of oil (from the supply pipe 34) passes through the chamber 59 and holes I00 to either side of the land 85 which is positioned centrally of the holes I00. At the same time an equal minute bleed of oil under pressure takes place through the discharge openings IOI, I02 to the annular chambers I03, I04, and the pipes 31 to the sump. Thus the system comprising the supply pipe 34, the space within the bore 58 between the lands 95, 98, the space within the bore 90 between the lands 98, '91, pipes 35, 35 and the two ends of the cylinder of the servo-motor are all maintained under an active uniform fluid pressure with no possibility for pressure build-up at one side of the piston of the servo-motor relative to the other side, or vice versa. I have found it highly desirable to provide (at neutral position of the valve member 80) such continuous minute passage of oil from the supply 34 through the pilot assembly to drain 31 to insure full equalization of pressure in all parts of the system.

2. When, upon change in pressure eflfective upon the bellows 21, the valve member 05 is moved upwardly, the land 90 forms an obstruction between the openings I00 and the openings I05, and the land 95 further opens the drainage holes IM to allow a bleed of fluid from the pipe 7 a openings I01 to the chamber I00 and pipe 35.

In the meantime the land 01 has moved to obsiu'uct drainage to the lower discharge opening I02. The degree of upward movement of the valve 05 determines the percentage opening of the holes and thus the speed of travel of the piston of the servo-motor.

3. Conversely, upon the valve being moved downwardly, connections to the drain openings I are closed, the drains I02 are opened and fluid under pressure from the supply 34' is-admitted to the pipe 26 and drained to the pipe 31 from .the pipe 35.

Axial location of the sleeve 81 relative to the pipes 34, 35 and '30 is readily apparent from the drawing Fig. 2. Axial adjustment of the valve member 05 relative to the sleeve 0'! for any given loading condition of pressure within the bellows 21 and loading of the spring 88 is accomplished by the adjustable connection to the ball joint 0| or 93.

This application is a division of my application Serial No. 524,707, filed March 2, 1944, now Patent No 2,475,326.

While I have illustrated and described certain preferred embodiments of my invention it will be understood that they are by way of example only and that I am not to be limited thereto except as defined in the following claims.

What I claim as new, and desire to secure by Letters Patent of the United States, is:

l. A hydraulic pilot valve comprising a housing, a sleeve body axially movable in the housing, a cylindrical chamber in the sleeve body having two spaced outlet ports, an inlet port located between said outlet ports, and a waste port located beyond each of said outlet ports, a movable valve member located axially in said chamber and journaled in fluid sealing manner in the ends of the pilot valve, said valve member provided with three spaced lands closely fitting the bore of the cylindrical chamber and spaced in general agreement with the inlet and two outlet ports, each of said lands having a diameter slightly less than the diameter of said cylindrical chamber to permit a minute fluid leakage therebetween, the center land being of an axial dimension slightly less than the inlet port so that there normally exists a minute fluid pressure flow from said inlet port past said center land to each of said waste ports, the two outermost lands having an axial dimension less than the waste ports to permit fluid communication between the waste ports and the portions of the cylindrical chamber outboard of the two outermost lands, the two outermost lands spaced a slightly greater amount than the minimum distance between the waste ports thereby normally allowing a slight fluid bleed to waste through each of said waste ports, whereby when the movable valve member is in neutral position the continuous fluid pressure feed from the inlet port to the two outlet ports and the continuous fluid pressure bleed to waste prevents the possibility of a build-up of pressure in one outlet port relative to the other, said housing having threaded end portions, end caps threadedlv engaging said threaded end portions and adapted to engage said sleeve body to thus effect longitudinal adjustment of said sleeve body relative to said housing.

2. A fluid pressure directing valve comprising a hollow housing with a sleeve body axially movable therein, said sleeve body having a wall defining a chamber therein, an inlet port in said sleeve body wall to direct fluid into said chamber, a' first waste port in -said sleeve body wall spaced in a first direction from said inlet port, a second waste port in said sleeve'body wall spaced in a second direction from the said inlet port, a valve member in said chamber reciprocably movable from a neutral position to a first and a second operating position, said valve member having a first land portion at one end thereof, a second land portion at the other end thereof, and a third land portion intermediate said first and second land portions, said first and third land portions in combination with the body wall defining a first compartment and said second and third land portions in combination with the body wall defining a second compartment, each ofsaid land portions having a transverse dimension slightly less than the transverse dimension of said chamber to permit a minute fluid leakage therebetween, said third land portion having an axial dimension less than the axial dimension of the inlet port,

said first and second land portions having an axial dimension less than the waste ports to permit fiuid communication between the waste ports and the portions of the chamber outboard of the first and second land portions, said first and second land portions .being spaced from each other a distance greater than the distance between the waste ports, whereby in the neutral position of said valve member the first and second compartments are in communication with the first and second waste ports respectively, a first outlet port in said body wall communicating with said first compartment and a second outlet port in said body wall communicating with said second compartment, said third land portion and said inlet port having wall means disposed relative to each other in said neutral position to define fluid passages to both said compartments, said third land portion and said inlet port having wall means disposed relative to each other in said first operating position to define a fluid passage from said inlet port to said first compartment and to obstruct fluid communication to said second compartment, and said third land portion and said inlet port having wall means disposed relative to each other in said second operating position to define a fluid passage to said second compartment and to obstruct fluid communication to said first compartment.

3. A fluid pressure directing valve comprising a hollow housing with a sleeve body axially movable therein, said sleeve body having a cylindrical wall defining a chamber therein, an inlet port in said sleeve body wall to direct fluid into said chamber, a first waste port in said sleeve body wall spaced in a first direction from said inlet port, a second waste port in said sleeve body wall spaced in a second direction from the said inlet port, a valve member in said chamber reciprocably movable from a neutral position to a first and second operating position, said valve member having a first cylindrical land portion at one end thereof having a cross section smaller than the cylindrical chamber to provide a bleed passage therebetween, a second cylindricalland portion at the other end thereof having a cross section smaller than the cylindrical chamber to provide a bleed passage therebetween, and a third cylindrical land portion intermediate said first and second land portions in combination with the body wall defining a second compartment, said first and second land portions having an axial dimension less than the waste ports to permit fluid communication between the waste ports and the portions of the cylindrical chamber outboard of the first and second land portions, said first and second land portions being spaced from each other a distance greater than the distance between the waste ports, whereby in the neutral position of said valve member the first and second compartments are in communication with the first and second waste ports respectively, a first outlet port in said body wall communicating with said first compartment and a second outlet port in said body wall communicating with said second compartment, said third land portion having an axial dimension less than theaxial dimension oi. the inlet port, said third land portion having a cross section smaller than the cylindrical chamber to define fluid passages with said inlet port to both said compartments, said third land portion and said inlet port having wall means disposed relative to each other in said first operating position to define a fiuid passage from said inlet port to said first compartment and to obstruct fluid communication to said second compartment, and said third land portion and said inlet port having wall means disposed relative to each other in said second operating position to define fluid passage to said second compartment and to obstruct fluid communication to said first compartment, said housing having threaded end portions, end caps threadedly engaging said threaded end portions and adapted to engage said sleeve body to thus effect longitudinal adjustment of said sleeve body relative to said housing.

4. A fluid pressure directing valve comprising a second waste port in said sleeve body wall spaced in a second direction from the said inlet port, a valve member in said chamber reciprocably movable from a neutral position to a first and second operating position, said valve member having a first cylindrical land portion at one end thereof having a cross section smaller than the cylindrical chamber to provide a bleed passageway therebetween, a second cylindrical land portion at the other end thereof having a cross section smaller than the cylindrical chamber to provide a bleed passageway therebetween, and a third cylindrical land portion intermediate said first and second land portions, said first and third land portions in combination with the body wall defining a first compartment and said second and third land portions in combination with the body wall defining a second compartment, said first and second land portions having an axial dimension less than the waste ports to permit fiuid communication between the waste ports and the portions of the cylindrical chamber outboard oi. the first and second land portions, said first and second land portions being spaced from each other a distance greater than the distance between the waste ports, whereby in the neutral position of said valve member the first and second compartments are in communication with the first and second waste ports respectively, a first outlet port in said body wall communicating with said first compartment and a second outlet in said body wall communicating with said second com.- partment, said third land portion having an annular surface the width of which is less than the diameter of said inlet port, said annular surface swam and said inlet port in said neutral position defining fluid passages to both said compartments, said third land portion and said inlet port having wall means disposed relative to each other in said first operating position to define a fluid passage to said first compartment and to obstruct -fiuid communication to said second compartment,

and said third land portion and said inlet port having wall means disposed relative to each other in said second operating position to define a fluid e to said second compartment and to obstruct fiuid communication to said first compartment, said housing having threaded end portions, end caps threadedly engaging said threaded end portions and adapted to engage said sleeve body to thus effect longitudinal adjustment of said sleeve body relative to said housing.

CLARENCE JOHNSON.

summons crrnn The following references are of record in the -fiie of this patent:

UNITED STATES PATENTS Number Number Date France May 30, 1927 

